1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel and a driving method thereof that is capable of improving discharge efficiency as well as preventing a crosstalk.
2. Description of the Related Art
Generally, a plasma display panel (PDP) is a display device utilizing a visible light emitted from a fluorescent body when an ultraviolet ray generated by a gas discharge excites the fluorescent body. The PDP has an advantage in that it has a thinner thickness and a lighter weight in comparison to the existent cathode ray tube (CRT) and is capable of realizing a high resolution and a large-scale screen. The PDP includes a plurality of discharge cells arranged in a matrix pattern, each of which makes one pixel of a field.
FIG. 1 is a perspective view showing a discharge cell structure of a conventional three-electrode, alternating current (AC) surface-discharge PDP.
Referring to FIG. 1, a discharge cell of the conventional three-electrode, AC surface-discharge PDP includes a scan/sustain electrode 12Y and a common sustain electrode 12Z provided on an upper substrate 10, and an address electrode 20X provided on a lower substrate 18.
The scan/sustain electrode 12Y and the common sustain electrode 12Z are transparent electrodes made from indium-tin-oxide (ITO). Since the ITO has a high resistance value, a signal is applied via bus electrodes 13YB and 13ZB to thereby apply an uniform voltage to each discharge cell
On the upper substrate 10 provided with the scan/sustain electrode 12Y and the common sustain electrode 12Z in parallel, an upper dielectric layer 14 and a protective film 16 are disposed. Wall charges generated by plasma discharge are accumulated on the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from magnesium oxide (MgO).
A lower dielectric layer 22, barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X. The surfaces of the lower dielectric layer 22 and the barrier ribs 24 are coated with a fluorescent layer 26. The address electrode 20X is formed in a direction crossing the scan/sustain electrode 12Y and the common sustain electrode 12Z.
The barrier rib 24 is formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells. The fluorescent layer 26 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive gas for a gas discharge is injected into a discharge space defined between the upper and lower substrate 10 and 18 and the barrier rib 24.
FIG. 2 represents an arrangement structure of the overall electrode lines and discharge cells of the PDP shown in FIG. 1.
Referring to FIG. 2, a discharge cell 28 is positioned at each intersection among the scan/sustain electrode lines Y, the common sustain electrode lines Z and the address electrode lines X. The outer edge of the scan/sustain electrode line Y and the common sustain electrode lines Z is provided with the bus electrodes YB and ZB. The barrier ribs 24 are formed in parallel to the address electrode lines X.
Such a three-electrode AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different emission number, so as to realize gray levels of a picture. Each sub-field is again divided into a reset period for uniformly causing a discharge, an address period for selecting the discharge cell and a sustain period for realizing the gray levels depending on the discharge number. When it is intended to display a picture of 256 gray levels, a frame interval equal to 1/60 second (i.e. 16.67 msec) is divided into 8 sub-fields. Each of the 8 sub-fields is divided into a reset period, an address period and a sustain period. The reset period and the address period of each sub-field are equal every sub-field, whereas the sustain period and the discharge number are increased at a ration of 2n (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. Since the sustain period becomes different at each sub-field as mentioned above, the gray levels of a picture can be expressed. In order to express the gray levels, driving waveforms as shown in FIG. 3 are applied to each electrode line of the PDP for each sub-field.
Referring to FIG. 3, one sub-field is divided into a reset period for initializing the entire field, an address period for scanning the entire field on a line-sequence basis to write a data, and a sustain period for keeping a light-emission state of the cells into which a data is written.
First, in the reset period, a reset pulse VR is applied to the common sustain electrode line Z to generate a reset discharge between the common sustain electrode line Z and the scan/sustain electrode line Y. When the reset discharge is generated between the common sustain electrode line Z and the scan/sustain electrode line Y, priming charged particles and wall charges are formed at each discharge cell.
In the address period, a scanning pulse −Vs is sequentially applied to the scan/sustain electrode lines Y, and a data pulse Vd synchronized with the scanning pulse −Vs is applied to the address electrode lines X. At this time, a desired level of direct current voltage for preventing an erroneous discharge is applied to the common sustain electrode lines Z.
In the sustain period, sustaining pulses Vsus having the same pulse width and voltage are alternately applied to the scan/sustain electrode lines Y and the common sustain electrode lines Z to make a sustain discharge of the discharge cells selected by an address discharge.
As described above, the conventional PDP allows sustaining pulses to be alternately applied to the scan/sustain electrode lines and the common sustain electrodes formed in adjacent to each other in the sustain period. For this reason, an erroneous discharge may be caused between the scan/sustain electrode lines and the common sustain electrodes formed adjacently with having the barrier ribs therebetween.
Further, since the scan/sustain electrode lines and the common sustain electrode lines are formed at the center of the discharge cell, the sustain discharge concentrates on the middle portion of the upper substrate to reduce a utility of the discharge space. In other words, a discharge area of the sustain discharge is reduced to cause a deterioration in the light-emission efficiency.
In addition, since the barrier ribs are formed in parallel to the address electrodes, a light generated at a specific discharge cell is provided at the upper/lower portion of the specific discharge cell. In other words, a crosstalk may be generated between the discharge cells arranged in a direction perpendicular to the barrier ribs.
In order to improve the discharge efficiency, there has been suggested a five-electrode, AC surface-discharge PDP as shown in FIG. 4.
Referring to FIG. 4, the conventional five-electrode, AC surface-discharge PDP includes first and second trigger electrodes 34Y and 34Z provided on an upper substrate 30 in such a manner to be positioned at the center of a discharge cell, first and second sustain electrodes 32Y and 32Z provided on the upper substrate 30 in such a manner to be positioned at the edge of the discharge cell, and an address electrode 42X provided at a lower substrate in a direction crossing the trigger electrodes 34Y and 34Z and the first and second sustain electrodes 32Y and 32Z.
On the upper substrate 30 provided with the first sustain electrode 32Y, the first trigger electrode 34Y, the second trigger electrode 34Z and the second sustain electrode 32Z in parallel, an upper dielectric layer 36 and a protective layer 38 are disposed. On the other hand, a lower dielectric layer 44 and a barrier rib 46 are formed on a lower substrate 40 provided with the address electrode 42X, and a fluorescent layer 48 is coated on the surfaces of the lower dielectric layer 44 and the barrier ribs 46.
The trigger electrodes 34Y and 34Z spaced at a narrow distance Ni at the center of the discharge cell are supplied with an alternating pulse in the sustain period to initiate a sustain discharge. The first and second sustain electrodes 32Y and 32Z spaced at a wide distance Wi at the edge of the discharge cell are used to keep a plasma discharge after the discharge was initiated by the trigger electrodes 34Y and 34Z.
An operation process of the five-electrode AC surface-discharge PDP will be described in detail with reference to FIG. 5 below. FIG. 5 is a section view representing a state of rotating the upper substrate by 90° with respect to the lower substrate so as to show up the overall electrode structure within one discharge cell.
First, in the reset period, a reset pulse is applied to the second trigger electrode 34Z of the discharge cell to generate a reset discharge for initializing the discharge cell.
In the address period, a scanning pulse is sequentially applied to the first trigger electrode 34Y and a data pulse synchronized with the scanning pulse is applied to the address electrode X. At this time, an address discharge is generated at the discharge cells supplied with a data.
In the sustain period, a first alternating current pulse is alternately applied to the first and second trigger electrodes 34Y and 34Z. Also, a second alternating current pulse having a higher voltage level than the first alternating current pulse is applied to the first and second electrodes 32Y and 32Z. When the first alternating current pulse is applied, a discharge is initiated between the first and second trigger electrodes 34Y and 34Z. At this time, the first and second sustain electrodes 32Y and 32Z generate a sustain discharge by a priming effect of charged particles caused by said discharge between the first and second trigger electrodes 34Y and 34Z.
In such a conventional five-electrode PDP, a sustain electrode is initiated by utilizing the trigger electrodes 34Y and 34Z, to thereby cause a sustain discharge having a long discharge path.
However, a sustaining pulse is alternately applied to the first and second sustain electrodes formed adjacently each other during the sustain period. Accordingly, an erroneous discharge may be generated between the first and second sustain electrodes formed in parallel with the barrier ribs therebetween.
Furthermore, since the barrier ribs are formed in parallel to the address electrode lines, a light generated at a specific discharge cell is applied to the discharge cells provided at the upper/lower portions of the specific discharge cell. In other words, a crosstalk may be generated between the discharge cells arranged in parallel in a direction perpendicular to the barrier ribs.